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(EX/P4-07) Global Particle Balance and Wall Recycling Properties of Long Duration Discharges on TRIAM-1M

M. Sakamoto1), M. Yuno1), S. Itoh1), K. Hanada1), K. Nakamura1), H. Zushi1), E. Jotaki1), M. Hasegawa1), S.V. Kulkarni2), A. Iyomasa1), S. Kawasaki1), H. Nakashima1)
1) Advanced Fusion Research Center, Research Institute for Applied Mechanics, Kyushu University, Kasuga, Japan
2) Institute for Plasma Research, Bhat, India

Abstract.  The longest plasma discharge with the duration of 3 h 10 min was achieved. The global particle balance of such long duration discharges has been investigated. In the longest discharge, H-alpha emission increased spontaneously around t$ \sim$30 min and the gas supply was automatically stopped. After that the plasma density was maintained by the recycling flux alone until the end of the discharge. Moreover, it has been observed that there exists a quite large difference between properties of wall recycling in the continuous gas feed case (i.e. static condition) and the additional gas puff case (i.e. dynamic condition). In the static condition, the effective particle confinement time increases almost linearly to about 10 s during 1 min of the discharge duration. In the dynamic condition, the decay time of the electron density just after the gas puff, i.e. the effective particle confinement time, is about 0.2 s during the 1min discharge. It is considered that the enhanced wall pumping is caused by the increase in fluxes of the diffused ions and charge exchange neutrals from the plasma to the wall due to the additional gas puff.

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IAEA 2003